This migration data website developed by Tax Foundation researcher Nick Kasprak with assistance provided by Gerald Prante provides an interactive way to analyze IRS data that shows how people and money flow across states. Because the Tax Foundation specializes in tax data and has received numerous requests for this type of data, we decided to develop this tool. The IRS data was not manipulated in any way by the Tax Foundation; we simply took the IRS data and developed this interactive tool that makes it easier for people to access the data.
A full description of the data from the IRS is available here.

Some cautions when using the data:

1. Net migration for some states like Florida and Arizona that attract retirees are kind of "inflated" by the fact that people move to those states at the latter stages of life and never leave. To be blunt, they die; and hence, they are never counted as out-migration from the state.

2. AGI figures understate the amount of income gain or loss that is the result of migration because it only counts the adjusted gross income of the migrant in the one year he/she moves. So for example, if Bob moved from Alabama to Georgia in 2000, the data would show Alabama as losing say $50,000 in AGI to Georgia in 2000. However, because income is a flow variable, Bob will be earning income in 2001, 2002, 2003 and so forth, which was also lost by Alabama to Georgia. The data doesn't count that "income loss" resulting in those years because Bob is no longer considered a migrant -- he's now a Georgia resident.

This problem doesn't really exists for the other two variables (returns and exemptions) except to the extent that people procreate following their migration.